Cannabinoids have long been known for their therapeutic potential in pain relief, treatment of seizures, antiemesis et cetera. It is, however, a class of compounds whose usage has been associated with a great deal of debate owing to its psychoactive effects. It was not until the discovery of cannabinoid receptors (CB1 and CB2) and the isolation of individual cannabinoids such as THC (tetrahydrocannabinol), CBD (cannabidiol), CBN (Cannabinol), and THCV (Tetrahydrocannabivarin), that the psychoactive effects could be attributed primarily to compounds (like THC) with high affinities to the receptor CB1. Furthermore, it has been established that individual cannabinoids differ from one another in their affinities to receptors and certain cannabinoids, such as CBD, behave as CB1/CB2 antagonists, thereby blocking some actions of their agonists, such as THC.
With on-going research, therapeutic applications of cannabinoids are becoming increasingly evident, resulting in legalisation of these compounds for medical purposes in a number of countries. The primary targets of research in this field are being associated with safe, rapid and/or effective delivery of cannabinoids.
A number of ways of delivering cannabinoids are known in the art.
For example, US2012/0304990 teaches the use of heating to vaporise a cannabis deposit.
One drawback of this system is that there is only a small temperature differential between the temperature at which the cannabis will vaporise (180° c. to 200° c.) and the temperature at which toxins are produced (230° c.).
A number of documents (for example WO03/055549, U.S. Pat. No. 6,509,005 and WO2004/000290) disclose the use of a metered dose inhaler. Such inhalers suffer from a number of drawbacks. Firstly, the metering chamber is relatively small, generally less than 100 μl resulting in delivery of fairly concentrated doses. Also, such devices require users to optimally co-ordinate actuation of the outlet valve and inhalation, failing which, dose delivery could be variable.
A further common mechanism is the simple spray which is disclosed, for example, in WO002/064109 and US2006/135599 which are designed to provide a sublingual or buccal spray. Such a spray is currently being marketed by GW Pharmaceuticals under the Sativex™ brand. These sprays suffer from the possibility of non-uniform drug dose delivery owing to the flushing action of saliva. Further, they have a slower onset of action when compared with pulmonary delivery.